1. Field of the Invention
The present invention relates to a method of manufacturing pre-stressed concrete members, which are reinforced with carbon fiber, useful as pillars, columns, spars, beams or the like of building, civil engineering or offshore structures and so on.
2. Description of the Related Art
Pillar, columns, spars, beams or the like in a building, constructing or engineering field are fabricated from concrete members reinforced with steel rods or fiber-reinforced plastics (FRP). Although the steel rod is a representative reinforcing member, it is heavy and requires a broad workspace for processing and handling the reinforced concrete member. The steel rod shall be stored in a properly controlled atmosphere due to its poor corrosion-resistance. Especially, a post-tension concrete member, which has the structure that steel anchors are embedded in a concrete body at both ends, is significantly damaged in a corrosive atmosphere near a seaside.
Application of thermosetting carbon fibers or fiber cables to pre-stressed concrete members has been researched and developed, aiming at lightening and improved corrosion-resistance of the concrete members. In fact, prepregs, which are prepared by bundling many carbon filaments of 10 μm or less in diameter and impregnating the fiber bundle with a thermosetting primer, are sometimes used as carbon fiber cables. Composite members, which are prepared by forming and curing a woven fiber bundle, are also used for reinforcement of concrete members.
Thermosetting carbon fibers and carbon fiber cables are very expensive due to complicated manufacturing process, so that concrete members reinforced with such fibers or cables can not be used to various fields in point of economical view. Carbon fiber cables are often embedded in a loosed state, resulting in poor fatigue strength of the concrete members. Moreover, steel anchors, which are likely to be damaged in a corrosive atmosphere, are still used for pre-stressed concrete members reinforced with carbon fiber cables. In short, corrosion of the concrete members in a salty atmosphere is not fundamentally dissolved only by use of thermosetting carbon fibers or carbon fiber cables for reinforcement.